The experiments of this proposal would examine whether similarities in the anatomical organization of vertebrate central visual systems indicate analogies in function. It is proposed to determine with behavioral methods retinal projection pathways necessary for wavelength discrimination in the 13-lined ground squirrel, Citellus tridecemlineatus and the frog, Rana pipiens. If it is found that more than one pathway is sufficient for wavelength discrimination it is proposed to determine how each contributes to the organization of this behavior. It is also proposed to examine some aspects of anatomical organization of central nervous system structures likely to be involved in wavelength discrimination in these two species.